Do you have more than one computer, or do you find yourself in situations where you use more than one computer regularly (such as work/home)? Do you use Firefox?
If so, you owe it to yourself to try Google Browser Sync. This slick little extension for Firefox allows you to syncronize certain aspects of the browser across multiple computers. With Browser Sync, you can unify bookmarks, cookies, history, passwords, tabs, and windows “automagically.”
This is very convenient for me, as syncing bookmarks saves a lot of importing and editing time across multiple systems, and being able to close a set of tabbed pages and home and open them at work is very slick.
It serves its purpose well, but I would like to see an option to syncronize more aspects of the browser, such as themes and other extensions. Perhaps this will be possible one day. Until then, Google Browser Sync is a highly useful extension that can save lots of manual tweaking time.